Temperature and Term Low Birth Weight in California

Area of Science:

• Environmental Health
• Reproductive Epidemiology
• Perinatal Outcomes

Background:

• Limited research exists on the impact of temperature on birth outcomes.
• Heat exposure during pregnancy is a growing concern with potential adverse effects.
• Understanding the relationship between heat and low birth weight (LBW) is crucial for public health.

Purpose of the Study:

• To investigate the association between apparent temperature and term low birth weight (LBW).
• To identify critical exposure windows and temperature thresholds for adverse birth outcomes.
• To examine differential risks among vulnerable maternal subgroups.

Main Methods:

• Retrospective cohort study of over 2 million births in California (1999-2013).
• Utilized birth certificate data and meteorological data (apparent temperature).
• Analyzed associations between apparent temperature metrics and term LBW, considering gestational windows and maternal factors.

Main Results:

• A 10°F increase in apparent temperature above 55°F was associated with a 13.0% increase in term LBW risk.
• Third-trimester exposure above 60°F showed the strongest association (15.8% increased risk).
• Black mothers, older mothers, male infants, and births during warmer seasons were at higher risk.

Conclusions:

• Elevated apparent temperature during pregnancy, particularly in the third trimester, is linked to increased term LBW.
• Vulnerable populations, including minority groups and those in warmer climates, require targeted interventions.
• Findings highlight the need for public health strategies to mitigate heat exposure risks during pregnancy.